U.S. patent number 5,856,539 [Application Number 08/751,570] was granted by the patent office on 1999-01-05 for fatty acid isomerisation.
This patent grant is currently assigned to Unichema Chemie B.V.. Invention is credited to William R. Hodgson, Wicher Tijmen Koetsier, Cornelis Martinus Lok, Glyn Roberts.
United States Patent |
5,856,539 |
Hodgson , et al. |
January 5, 1999 |
Fatty acid isomerisation
Abstract
It was found that the conversion (by isomerisation or branching)
of unsaturated fatty acids into branched fatty acids can be
catalysed by materials having a microporous structure. Such a
process gives high conversion rates and a high selectivity towards
branched fatty acids, whilst a low amount of undesired by-products
is obtained. Zeolites are preferred materials for catalysing said
reaction.
Inventors: |
Hodgson; William R. (Bebington
Wirral, GB3), Koetsier; Wicher Tijmen (Emmerich,
DE), Lok; Cornelis Martinus (Bebington Wirral,
GB3), Roberts; Glyn (Bebington, GB3) |
Assignee: |
Unichema Chemie B.V. (Gouda,
NL)
|
Family
ID: |
8221399 |
Appl.
No.: |
08/751,570 |
Filed: |
November 18, 1996 |
Foreign Application Priority Data
|
|
|
|
|
Nov 16, 1995 [EP] |
|
|
95308224 |
|
Current U.S.
Class: |
554/125 |
Current CPC
Class: |
C07C
51/353 (20130101); C07B 37/08 (20130101); Y02P
20/582 (20151101) |
Current International
Class: |
C07B
37/08 (20060101); C07B 37/00 (20060101); C07C
51/347 (20060101); C07C 51/353 (20060101); C07C
051/353 () |
Field of
Search: |
;554/125 |
Foreign Patent Documents
|
|
|
|
|
|
|
0 683 150 A1 |
|
Nov 1995 |
|
EP |
|
WO 91/06616 |
|
May 1991 |
|
WO |
|
Primary Examiner: Killos; Paul J.
Attorney, Agent or Firm: Pillsbury Madison & Sutro
LLP
Claims
We claim:
1. In a process for the isomerisation of fatty acids, in which a
fatty acid feed comprising unsaturated fatty acids is contacted
with a catalyst, the improvement wherein the catalyst comprises a
material having a microporous structure.
2. Process according to claim 1, wherein the isomerisation of fatty
acids comprises branching of the fatty acids.
3. Process according to claim 1, wherein the material having a
microporous structure comprises a zeolite.
4. Process according to claim 1, wherein the zeolite comprises a
zeolite having a uni-dimensional pore system.
5. Process according to claim 3 or 4, wherein the zeolite comprises
mordenite, zeolite L and/or zeolite omega.
6. Process according to claim 5, wherein the ratio of SiO.sub.2
/Al.sub.2 O.sub.3 in the mordenite is at least 14, and more
preferably at least 20, and most preferably at least 35.
7. Process according to claim 1, wherein the fatty acid feed
comprises of at least 50% by weight of unsaturated fatty acids.
8. Process according to claim 7, wherein the fatty acid feed
comprises of at least 80% by weight of unsaturated fatty acids.
9. Process according to claim 1, wherein the fatty acid feed
comprises at least 40% by weight of oleic acid.
10. Process according to claim 9, wherein the fatty acid feed
comprises of at least 70% by weight oleic acid.
11. Process according to claim 1, wherein at least part of the
isomerisation is performed at a temperature of between 200.degree.
C. and 320.degree. C.
12. Process according to claim 11, wherein at least part of the
isomerisation is carried out at a temperature of between
230.degree. C. and 285.degree. C.
13. Process according to claim 1, wherein the fatty acid feed is
contacted with the catalyst for a period of at least 30
minutes.
14. Process according to claim 13, wherein the fatty acid feed is
contacted with the catalyst for a period of 1-16 hours.
15. Process according to claim 1, wherein the catalyst is reused
without reactivation.
16. Process according to claim 1, wherein the catalyst is reused
following reactivation.
17. Process according to claim 1, wherein the amount of catalyst
used is between 0.5 and 20% by weight.
18. Process according to claim 17, wherein the amount of catalyst
used is between 3 and 7% by weight.
19. Process according to claim 1, wherein the ratio L/D, wherein L
refers to the the maximum crystallite diameter and D to the maximum
crystallite depth of the zeolite cystallites, is larger than 8.
20. Process according to claim 19, wherein the ratio L/D is at
least 10.
21. Process according to claim 20, wherein the ratio L/D is at
least 20.
22. In a process for the isomerisation of fatty acids, in which a
fatty acid feed comprising unsaturated fatty acids is contacted
with a catalyst, the improvement wherein the catalyst comprises a
zeolite material having a microporous structure whereby said feed
is converted into a mixture which is rich in branched fatty acids
and low in oligomers.
Description
The present invention relates to a chemical process, and in
particular to a process for the isomerisation (branching) of fatty
acids in which a catalyst is employed. In said process, the fatty
acid feed to be processed comprises unsaturated fatty acids.
Fatty acids are versatile building blocks in various parts of the
chemical industry, ranging from lubricants, polymers, solvents to
cosmetics and much more. Fatty acids are generally obtained by
hydrolysis of triglycerides of vegetable or animal origin.
Naturally occurring triglycerides are esters of glycerol and
generally straight chain, even numbered carboxylic acids, in size
ranging from 10-24 carbon atoms. Most common are fatty acids having
12, 14, 16 or 18 carbon atoms. The fatty acids can either be
saturated or contain one or more unsaturated bonds.
Long, straight chain saturated fatty acids (C10:0 and higher) are
solid at room temperature, which makes them difficult to process in
a number of applications. The unsaturated long chain fatty acids
like e.g. oleic acid are liquid at room temperature, so are easy to
process, but are unstable because of the existence of double
bond(s). Branched fatty acids mimic the properties of the straight
chain unsaturated fatty acids in many respects. However, they do
not have the disadvantage of being unstable. For example branched
C18:0 fatty acid (commercially known as isostearic acid) is liquid
at room temperature, but is not as unstable as C18:1, since
unsaturated bonds are absent in branched C18:0. Therefore, branched
fatty acids are for many applications more desirable than straight
chain fatty acids. (The term "branched fatty acids" is herein to be
understood to comprise fatty acids which contain one or more alkyl
side groups, which can be attached to the carbon chain at any
position. Said alkyl groups are generally short.)
Currently, branched fatty acids are obtained by isomerisation
(branching) of the straight chain, unsaturated fatty acids having a
corresponding chain length. For example, branched C18:0 is prepared
from straight C18:1 (or also C18:2).
Among the routes known for said isomerisation or branching is a
reaction in which clay is used as a catalyst. This clay catalysed
isomerisation suffers from two main disadvantages, the most
important one being the fact that besides the formation of the
desired branched fatty acids, a considerable amount of undesired
side products (containing oligomers, saturated straight chain fatty
acids and intermediate dimers) is formed (30-40% by weight). The
formation of intermediate dimer is particularly disadvantageous,
since these represent very low value products. A second
disadvantage is that the clay catalyst cannot be reused.
Hence, there is a need for a new process overcoming these
disadvantages, i.e. a process for the preparation of branched fatty
acids from straight chain unsaturated fatty acid feedstocks with an
increased selectivity towards branched monomeric isomers versus
oligomeric species. Such a process should preferably still give
high conversion of reactants and employ a reusable catalyst.
It has now been found that it is possible to convert (by
isomerisation) a feed of fatty acids comprising fatty acids
containing at least one unsaturated carbon-carbon bond (such as
e.g. oleic acid) into a mixture which is rich in branched fatty
acids and low in oligomers. Preferably, the isomerisation involves
branching. In said process a fatty acid feed comprising unsaturated
fatty acids is contacted with a catalyst, characterized in that the
catalyst comprises a material having a microporous structure. It is
herein to be understood that the reaction product will generally
comprise both saturated as well as unsaturated branched fatty
acids, and both are thus included in the invention. Optionally, the
unsaturated branched fatty acids may be hydrogenated in any
conventional way. The reaction which is the subject of this
invention can be seen as an isomerisation reaction (involving both
skeletal and positional isomerisation). The branching reaction is
herein included.
Such a material having a microporous structure includes zeolites
and microporous materials having a zeolite structure such as
aluminium phosphates (AlPO's), metal aluminophosphates (MeAPO's)
and silico alumino phosphates (SAPO's). Zeolites are for the
purpose of this invention preferred.
Preferably, the zeolite in said process posesses a unidimensional
pore topology. A preferred zeolite of this type is mordenite.
Zeolites are crystalline aluminosilicates which can be represented
by the general formula M.sub.p/n [AlO.sub.2).sub.p
(SiO.sub.2).sub.192-p ].qH.sub.2 O, where M is a metal cation of
groups IA (including Hydrogen) or IIA and n is the valency of this
metal. Zeolites consist of a microporous network of SiO.sub.4 and
AlO.sub.4 tetrahedra linked together via shared oxygen atoms.
Aluminum has a 3+ valency resulting in an excess negative charge on
the AlO.sub.4 tetrahedra, which can be compensated by H.sup.+ or
other cations (Na.sup.+, NH.sub.4+, Ca.sup.2+). When M is hydrogen
the materials are Bronsted acidic, when M is for example Cs the
materials are basic. Upon heating, Bronsted acidic hydroxyls
condense creating coordinately unsaturated Al, which acts as a
Lewis acid site. The acid strength, acid site density and Bronsted
versus Lewis acidity are determined by the level of framework
aluminium. The ratio of silica/alumina can be varied for a given
class of zeolites either by controlled calcination, with or without
the presence of steam, optionally followed by extraction of the
resulting extraframework aluminium or by chemical treatment
employing for example ammonium hexafluorosilicate. It has been
found that, when mordenite is used as a catalyst, for achieving the
desired branched fatty acid selectivity whilst maintaining a good
conversion of unsaturated fatty acids, the ratio of SiO.sub.2
/Al.sub.2 O.sub.3 in the mordenite is preferably at least 14, more
preferably at least 20, and most preferably at least 35 (said ratio
was measured using X-ray fluorescence).
Another preferred class of zeolites for performing the reaction
according to the invention are the zeolites belonging to the
classes of zeolites L and zeolite omega. Zeolites L (including
their preparation) have been described in WO 91/06367. Zeolites
omega have been described in GB 1,178,186.
It has been found that for good selectivity whilst maintaining a
good conversion it is preferred that at least part of the
isomerisation is performed at a temperature of between 200.degree.
C. and 320.degree. C., and more preferably a temperature of between
230.degree. C. and 285.degree. C. Since the conversion is also a
function of the reaction time, it is preferred that the fatty acid
feed is contacted with the catalyst for a period of at least 30
minutes. More preferred are reaction times of 1-16 hours. In
general, the amount of catalyst employed in the process according
to the invention is between 0.5 and 20% by weight, based on the
total reaction mixture. More preferably is an amount of catalyst
used between 2.5 and 10% by weight. Most preferred are amounts
between 3 and 7% by weight.
In EP-A 683 150 it is mentioned that reactions similar to the
reaction according to this invention should be carried out in the
presence of water or a lower alcohol. However, applicants have
found that this is not always needed. Hence, it may be preferred to
perform the reaction as set out above, without adding water or a
lower alcohol, or, alternatively, in the absence of water or a
lower alcohol.
It has been found that by using the catalyst system according to
this invention it is possible to reuse the catalyst after a first
reaction cycle. In some cases it may be desired to add fresh
catalyst (while bleeding off part of the used catalyst), and in
other cases regeneration of the catalyst may be desired.
Regeneration can be effected by heating the used catalyst in an
inert atmophere (e.g. nitrogen) to 450.degree.-650.degree. C.
(preferably to about 550.degree. C.), although controlled oxidative
regeneration may be employed too. Regeneration may be effected by
washing with a solvent.
Since the process according to the invention is designed for
isomerisation or conversion of unsaturated fatty acids into
branched fatty acids, it is beneficial if the fatty acid feed
comprises of at least 50% by weight of unsaturated fatty acids,
more preferably at least 80% by weight of unsaturated fatty acids.
A preferred unsaturated fatty acid to be present in the fatty acid
feed is oleic acid. It is preferred that the fatty acid feed
comprises at least 40% by weight of oleic acid, more preferably at
least 70% by weight oleic acid. The feedstock may comprise
polyunsaturated fatty acids.
Applicants have furthermore found that for carrying out the process
according to the invention it is preferred that in the case in
which the catalyst employed is a zeolite, the morphology and/or
crystallite size of the zeolite material in addition to pore
topology are of importance.
As indicated before, zeolites having uni-dimensional pores are
preferred. Such zeolites are also described as having a linear pore
structure. Even more surprising than the influence of the pore
geometry is the fact that the shape or morphology of the zeolite
crystallites is of importance. The crystallite morphology can
accurately be quantified by measuring the crystallite diameter and
the crystallite depth. Most suitable for comparison purposes is
measurement of the maximum crystallite diameter (L) and the maximum
crystallite depth (D). These can be measured using (a combination
of) scanning electron microscopy (SEM) and/or transmission electron
microscopy (TEM). How this can be done is set out in detail in WO
91/06367. From the measured L and D values, both in micrometer, one
can calculate the aspect ratio L/D.
It has surprisingly been found that for good results (in terms of
optimal reactivity and low amounts of trimer and oligomers formed)
it may be preferred that the L/D ratio (crystallite aspect ratio)
is larger than 8. More preferably, this ratio should be larger than
12. It is even more preferred that this ratio is at least 10, and
it is most preferred that this ratio is at least 20.
The invention will be illustrated by the following examples, which
should not be interpreted as limiting the scope of the invention
thereto.
EXAMPLE 1:
Evaluation of commercial mordenites.
A feedstock essentially consisting of (percentages by weight):
97.4% C18:1 (oleic acid)
4.0% C16:0
1.3% C14:0
trace C18:0
was subjected to a range of isomerisation experiments.
Evaluation Procedure
In a one-litre Parr autoclave were mixed: 300 grams of feedstock
and the desired amount of the chosen catalyst. The reactor was
evacuated with nitrogen, and subsequently heated to the desired
temperature. The evacuating step involves pressurising the reactor
to 5 bar and stirring at 600 rpm followed by releasing the
pressure. This procedure was repeated twice with the reaction
vessel finally pressurized to 1 atmosphere with nitrogen. The
reactor is then maintained at the reaction temperature for the
chosen reaction time, whereafter the reactor is cooled to room
temperature.
The amount of catalyst ranged from 1.3 to 5% by weight. The
temperature ranged from 250.degree. C. to 275.degree. C. The
reaction time ranged from 1 to 6 hours.
The clay used was a naturally occurring montmorillonite clay,
composition SiO.sub.2 (64 w/w %), Al.sub.2 O.sub.3 (17 w/w %),
Fe.sub.2 O.sub.3 (5 w/w %), CaO(1.5 w/w %), MgO(4 w/w %). The
mordenite used was of formula: Na.sub.2 O.Al.sub.2
O.sub.3.10SiO.sub.2.6H.sub.2 O, type CBV10AH as marketed by PQ
(USA). Other types tested were CBV20A and CBV 30A (see table
2).
Analysis of the product mix was performed by first converting the
monomer, dimer and trimer mixture into its methyl derivatives by
refluxing in a BF.sub.3 /methanol mixture (12 w/w % BF.sub.3
--ex-Aldrich). The procedure for performing the derivatisation
involved weighing approximately 0.15 g of the total product into a
50 ml round bottomed flask. To this was added 2 ml of the BF.sub.3
/methanol complex and the mixture was heated to reflux, in a
standard water condenser/reaction flask arrangement, for 2 minutes.
Two mls of heptane was added to the flask via the condenser and
refluxed for a further two minutes. Following this, the mixture was
allowed to cool to room temperature, at which point sufficient
saturated NaCl solution was added to bring the resultant methylated
esters into the neck of the flask. The organic/methylated layer was
then transferred by pipette into a sample tube containing anhydrous
sodium sulphate and diluted to five times it's volume with heptane,
and the resultant mixture filtered.
The methyl esters were evaluated with a gas chromatograph equipped
with a flame ionisation detector and fitted with a J&W
Scientific 15 w 0.32 widebore DB5HT capillary column. Analysis of
the concentration of branched fatty acids present in the monomer
fraction was performed by first distilling approximately 20 mls of
total product in a "Kugelrohr" apparatus. The distillation was
carried out under a strong vacuum at 250.degree. C. Once the
desired temperature was reached the distillation was allowed to
continue for about 10 minutes to ensure all the monomer has been
distilled off. The monomer was collected and diluted in heptane
(1:10) ready for analysis. Analysis was performed with a gas
chromatograph fitted with a J&W Scientific 30m 0.25 narrowbore
FFAP column with a film thickness of 0.25 microns.
Results
The values of isostearic acid (ISA) obtained were calculated using
the following expression:
where the ratio [ISA/Monomer] refers to the concentration of
isostearic acid (w/w %) present in the distilled monomer fraction
and [Monomer].sub.TP is the concentration of monomer (w/w %)
present in the total product following esterification.
Similarly the levels of oleic and stearic acid are calculated using
the following expressions:
Stearic acid (w/w %)={[Stearic
acid]/[Monomer]}.times.[Monomer].sub.TP
The results are set out in tables 1, 2 and 3. In the tables, the
following codes are used:
ISA: isostearic acid (branched C18, including saturated and
unsaturated isostearic acid).
StA: stearic acid (C18:0, straight chain)
OA: oleic acid (C18:1, straight chain)
ID: intermediate dimer (mixture of partly dimerized, partly
branched, but containing more than 18 carbon atoms)
DIM: Dimers (C36 dibasic acids)
TRIM: Trimers (C54 tribasic acids).
In table 1, the mixtures obtained using clay and mordenite as a
catalyst system can be compared. The catalyst loading (amount of of
clay/zeolite) was 5% by weight. As can be seen, the use of
mordenite leads to the formation of low amount(s) of oligomers.
Regarding the use of mordenite, the influence of temperature and
reaction time can also be seen in table 1. In table 2 (also
catalyst loading 5% by weight), the influence of the silica:alumina
ratio can be seen. In table 3, the influence of using different
loadings of mordenite catalyst can be observed.
EXAMPLE 2:
Effect of Re-use of Catalyst.
In a set up identical to example 1 above, various re-use procedures
have been tested. Re-use has been performed on mordenite
CBV30A.
Re-use has been tested without reactivating the catalyst employed
between two cycles. After a first cycle, the catalyst was obtained
from the reaction medium by centrifuging the catalyst from the
total product, whereafter the reaction was started again, using
fresh oleic acid. Thermal analysis (TGA) on the centrifuged product
showed that the centrifuged catalyst contained about 35% solid and
about 65% residual total product. Thus, in order to have 15.8% of
mordenite catalyst, 45 g of the centrifuged product was added to
300 g of oleic acid.
Re-use has been performed for reaction times of 4 hours (similar to
example 1) and also for reaction times of 8 hours. Also, a re-use
cycle has been performed in which part of the catalyst was re-used
(90%), the remainder being replaced with fresh catalyst. The
results are displayed in table 4.
EXAMPLE 3:
Evaluation of Zeolites L and Omega.
In a process identical to the process for testing the mordenite
catalysts (example 1) three other uni-dimensional catalysts have
been tested: zeolite Omega and zeolite L, the latter in two forms:
HL1 and HL2. Zeolite Omega has been prepared according to the
process as disclosed in GB 1178186. Both zeolites L have been
prepared according to the process of Aeillo and Barrer, J. Chem.
Soc., A, 1470 (1970), see also example 4 below. Zeolite HL1 was
prepared under stirred conditions, HL2 under static conditions. The
zeolites L (HL1 and HL2) and omega were prior to use ion exchanged,
in order to yield the proton form of the zeolite. This procedure
involved refluxing 20 g of zeolite in 200 ml of 0.5M ammonium
chloride solution for 2 hours. The resultant slurry was allowed to
cool to room temperature and then filtered and washed with 3 litres
of boiling demineralised water. This process was repeated twice and
the resultant zeolite dried at 100.degree. C. overnight. Prior to
catalytic evaluation, all of the zeolite were calcined at
400.degree. C. for 1 hour in a shallow bed. This latter procedure
leads to decomposition of the ammonium ion to yield the proton form
of the zeolite and also results in water removal from the zeolite
pore channels.
The process used for evaluating the catalyst was identical as in
example 1, with the following settings:
amount of zeolite: 7.9 g (2.5% by weight)
reaction temperature: 250.degree. C.
reaction duration: 4 hours.
Analysis of the obtained reaction product was performed in the same
manner as in example 1. The results of the analysis are shown in
table 5.
EXAMPLE 4:
Effect of Uni-dimensional Zeolite Crystal Morphology.
Zeolite HL1
K form zeolite L was prepared using the recipe described by Aeillo
and Barrer, J. Chem. Soc., A, 1470 (1970). The procedure involves
adding 51.6 g of potassium hydroxide, 2.75 g aluminium wire, 61.4 g
fumed silica (CARBOSIL M5) and 284.5 g of distilled water into a
Teflon autoclave liner and mixing thoroughly. The resultant gel was
then aged at 100.degree. C. in a sealed autoclave for 9 days, in
order to affect crystallisation. Following crystallisation the
slurry was centrifuged at 3000 rpm for 30 mins, in order to
separate the zeolite form the mother liquor. The resultant zeolite
was washed with demineralised water and re-centrifuged at 3000 rpm
for a further 30 mins. This yielded a zeolite with the following
molar composition.
Zeolite HL2
K form zeolite L was prepared using the recipe described by Aeillo
and Barrer, J. Chem. Soc., A, 1470 (1970). The procedure involves
adding 51.6 g of potassium hydroxide, 2.75 g aluminium wire, 61.4 g
fumed silica (CARBOSIL M5) and 284.5 g of distilled water into a
Teflon autoclave liner and mixing thoroughly. The resultant gel was
then aged at 100.degree. C. with continual stirring at 300 rpm, in
a sealed autoclave for 8 days, in order to affect crystallisation.
Following crystallisation the slurry was centrifuged at 3000 rpm
for 30 mins, in order to separate the zeolite form the mother
liquor. The resultant zeolite was then washed with demineralised
water and re-centrifuged at 3000 rpm for a further 30 mins. This
yielded a zeolite with the following molar composition.
Zeolite HL3
A sample of zeolite L was prepared according to the method
described by Verduijn, EP-A 219 354. This method involves
dissolving aluminium hydroxide in a boiling aqueous solution of
potassium hydroxide pellets (86% pure KOH) to yield solution A.
After dissolution water loss was corrected by addition of
demineralised water. A separate solution, solution B, was prepared
by diluting colloidal silica (Ludox HS40) with water.
The two solutions were mixed for two mins to form a gel, and just
before the gel became fully set, the mixture was transferred to a
Teflon-lined autoclave, preheated to 150.degree. C. The autoclave
was maintained at this temp for 72 h to affect crystallisation.
Following crystallisation the slurry was centrifuged at 3000 rpm
for 30 mins, in order to separate the zeolite form the mother
liquor. The resultant zeolite was then washed with demineralised
water and re-centrifuged at 3000 rpm for a further 30 mins. This
yielded a zeolite with the following molar composition.
Zeolite HL4
A sample of zeolite L was prepared according to the method
described by Verduijn, WO 91/06367. This method involves dissolving
7.91 g of aluminium hydroxide in a boiling aqueous solution of KOH.
The latter was prepared by dissolving 34.30 g of KOH pellets in
50.10 g of water. The KOH/Al(OH).sub.3 solution (denoted solution
A) was allowed to cool to room temperature prior to further
experimentation A separate solution was prepared by adding 150.26 g
of colloidal silica (Ludox HS--40) and 50.01 g of water . To this
was added a solution prepared by dissolving 0.1 g of Ba(OH).sub.2
8H.sub.2 O crystals in 25 g of water. The resultant solution was
stirred for 5 mins and solution A added, together with 64.47 g of
water. The mixture was stirred for a further 3 mins and the
resultant synthesis mixture transferred to a stainless steel
autoclave. The autoclave was placed in an oven and heated to
170.degree. C. and maintained at this temperature for 96 hrs.
The product was separated from the mixture by centrifuging, washed
to pH 9.7 and dried overnight at 150.degree. C. This yielded a
zeolite L with the following composition.
Zeolite HL5 and zeolite HL6
In addition to the synthesised materials, two further L form
zeolites were obtained from commercial suppliers (HSZ-500KOA
(ex-Tosoh Corporation)--denoted HL5 in this study and Zeocat L
(ex-Uetikon)--denoted HL6.
All of the above samples were ion-exchanged in order to yield the
proton form of the zeolite. The procedure adopted involved
refluxing 20 g of the chosen zeolites in 200 ml of 0.5M ammonium
chloride solution for 2 h. The resultant slurry was allowed to cool
to room temperature and then filtered and washed with 3 litres of
boiling water. The process was repeated twice and the resultant
zeolite dried at 400.degree. C. for 1 h in a shallow bed in order
to decompose the the ammonium ion and yield the zeolite in the
proton form. Following ion--exchange the zeolites are hereafter
referred to as HL1-6, where the number refers to the example
aboves.
X-ray diffraction confirmed that all these materials were zeolite L
structures, while .sup.27 Al NMR studies confirmed that in excess
of 90% of the aluminium was present within the framework of the
zeolites.
Mordenites
Commercial mordenites were also evaluated, these comprised CBV30A
and CBV20A (ex-PQ) and HSZ620HOA, HSZ640HOA, and HSZ690HOA
(ex-Tosoh Corporation). All of these are supplied in the proton
form and were characterised and evaluated without additional
treatments.
X-ray diffraction confirmed that all these materials possessed
mordenite structures, while .sup.27 Al NMR studies confirmed that
in excess of 85% of the aluminium was present within the framework
of the zeolites.
The morphologies and crystallite sizes determined by a combination
of scanning electron microscopy (SEM) and transmission electron
microscopy (TEM) are summarised in Table 6. L refers to the maximum
crystallite diameter, D to the maximum crystallite depth and the
parameter L/D (diameter/depth) is the aspect ratio for the
crystals.
Scanning electron microscopy (SEM) was perfomed on all samples
following carbon coating, using a Cambridge S360 electron
microscope. Transmission electron microscopy (TEM) was performed on
a JEOL200CX transmission electron microscope at 80 kV following
dispersal of the sample in isopropanol.
The aspect ratios for the mordenites were found to vary from
1.5-10, while those of the L zeolites varied from 0.25-20.
Catalyst evaluaton in fatty acid branching/ oligomerisation
All of the catalysts were evaluated exactly as described in the
evaluation procedure as above in example 1. Catalyst concentrations
(loading) were 2.5 w/w % for all catalysts. A summary of the
obtained selectivities is given in Table 7. In table 7, the same
headings are the same as those used in Table 1.
TABLE 1
__________________________________________________________________________
Yields comparing clay with unidimensional zeolite (CBV10AH)
(Mordenite catalyst loading 5%) temp catalyst time (h) (.degree.C.)
% ISA % StA % OA % ID % DIM % TRIM
__________________________________________________________________________
clay 4 250 46 12 7 6 29 4 mordenite 4 250 53 12 20 7 11 0.6
mordenite 4 265 68 14 7 2 8 <0.1 mordenite 4 275 60 26 7 0.5 7
<0.1 mordenite 6 250 66 15 10 1 8 0.1
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
Yields using mordenite (catalyst loading 5% by weight), different
ratios of SiO.sub.2 /Al.sub.2 O.sub.3 SiO.sub.2 / Al.sub.2 O.sub.3
ratio of temp mordenite time (h) (.degree.C.) % ISA % StA % OA % ID
% DIM % TRIM
__________________________________________________________________________
14 4 250 16 6 61 8 9 0.1 (CBV10AH) 20 4 250 37 7 36 11 8 0.3
(CBV20A) 35 4 250 53 12 20 7 11 0.6 (CBV30A)
__________________________________________________________________________
TABLE 3 ______________________________________ The effect of
catalyst loading (Mordenite CBV30A, 4h, 250.degree. C.) Catalyst
loading (w/w %) % ISA % StA % OA % ID % DIM % TRIM
______________________________________ 5.0 53 12 20 7 11 0.6 2.5 48
8 36 0 9.0 0.2 1.3 25 7 58 0 9.5 0.2
______________________________________
TABLE 4 ______________________________________ The effect of
catalyst re-use, without reactivation (Mordenite CBV30A) time % % %
Process (h) ISA StA % OA % ID % DIM TRIM
______________________________________ no re-use 4 53 12 20 7 11
0.6 straight re-use 4 40 9 34 8 9 0.2 straight re-use 8 51 11 18 10
10 0.3 90% re-used, 4 48 10 24 8 10 0.4 10% fresh
______________________________________
TABLE 5 ______________________________________ Yields comparing
various unidimensional zeolites (loading 2.5%). Catalyst type % ISA
% StA % OA % ID % DIM % TRIM ______________________________________
Omega 24 9 42 19 6 trace HL1 51 14 16 18 3 -- HL2 51 13 10 18 9 --
______________________________________
TABLE 6 ______________________________________ Summary of
morphology and crystallite dimensions as determined by a
combination of SEM and TEM. Catalyst Morphology L/.mu.m D/.mu.m L/D
______________________________________ M30A Flat hexagonal 1.0 0.1
10 discs M20A Flat hexagonal 1.0 0.1 10 discs 620HOA Hexagonal
discs 5.0 2.5 2 640HOA Hexagonal discs 5.0 2.0 2.5 690HOA Mostly
Cubic 2.0 0.25 8 crystals with some needlelike crystals HL1 Flat
circular 1.0 0.05 20 plates HL2 Irregular 0.5 0.05 10 particles HL3
Cylinders 0.2 0.8 0.25 HL4 Flat plates and 2.0 0.5 4 needles HL5
Flat circular 0.5 0.1 5 discs HL6 Cylinders 2.0 2.0 1
______________________________________
TABLE 7 ______________________________________ Summary of %
isostearic acid, stearic acid, oleic acid, intermediate dimer,
dimer and trimer obtained using various mordenite and L zeolites as
catalysts. Catalyst % ISA % SA % OA % ID % DIM % TRIM
______________________________________ M30A 48 13 30 -- 9 trace
M20A 30 6 57 -- 7 trace 620HOA 2 -- 94 -- 4 -- 640HOA 9 3 83 -- 5
-- 690HOA 1 -- 97 -- 2 -- HL1 51 14 16 18 3 -- HL2 51 13 10 18 9 --
HL3 4 2 89 -- 6 -- HL4 2 1 94 -- 3 -- HL5 3 4 84 -- 9 0.4 HL6 3 0
91 -- 5 0.4 ______________________________________
* * * * *